Referring to FIG. 7, a prior nail is illustrated. In that, the stop plate 91, guide plate 93 and nail recess 92 are fixed together. The depth of the moving groove 94 is also fixed. Therefore, the box nailing machine only jets nails of fixing thickness. If nails of different thickness are to be used, the whole nail cartridge 9 must be updated, however, this is time and labor-consumed. Therefore, it is necessary to have a novel box nailing machine which may jet nails of different thickness without needing to update nail cartridge.